Large-Scale Edge Waves Generated by Hurricane Landfall

知识价值：飓风在沿海地区引发的风暴潮和洪水是一个重要的社会问题。在直接登陆区域以外和登陆后几小时内，自由传播的波脉冲可能会引起严重的洪水。这种情况过去确实发生过。2005年10月24日，飓风“威尔玛”登陆美国佛罗里达州西海岸后引发的风暴潮观测显示，当“威尔玛”向内陆移动时，风暴潮形成了一个波脉冲，风暴潮不再受到风力的影响。在退潮后的海平面资料中，波脉冲的高度超过1.5 m，但由于其在退潮时传播，在浪涌测量中有些模糊。该波脉冲持续时间约6小时，传播速度在10 ~ 25 m s-1范围内变化，表明初始扰动的演化过程。将波脉冲识别为具有大时空尺度的边波。这种由大陆架上的飓风引起的持续时间相对较短的波浪以前没有报道过。最有可能的是，它们没有被探测到，因为NOAA和USGS维持的标准观测网络中的稀疏空间分辨率无法解析它们的相位传播。相反，以前的研究集中在频率较低的海岸捕获波（CTW）上，其周期与惯性波相当或更长，这被认为是热带气旋产生的盛行波模式。本项目将采用面向过程的数值模拟方法研究飓风边缘波的产生和沿岸演变。更具体地说，将解决以下问题：-飓风登陆时产生边缘波的最有利条件是什么？飓风的大小，强度，平移速度和轨迹的作用，以及陆架地形的作用，将被描绘。-什么地形形式会引起边缘波的局部放大？大的地形变化（扩大/缩小大陆架，弯曲的海岸线等）和较小的特征（入口，河口，海角等）的影响将被系统地研究。-边波耗散的机制是什么？耗散主要与底部摩擦有关还是与近海能量辐射有关？更广泛的影响：该项目的成果将应用于国家和地区安全领域，如减灾、防灾和早期预警系统的发展。研究结果对沿海地区的管理和保护以及海上作业也很重要。本项目将资助一名研究生。

Intellectual merit:The hurricane-induced surge and flooding in the coastal areas is an important societal problem. Severe flooding outside the immediate landfall area and a few hours after the landfall can be caused by a freely propagating wave pulse. The cases indeed occurred in the past. The observations of the storm surge induced by Hurricane Wilma landfall on the West Coast of Florida on October 24, 2005 revealed a formation of a wave pulse as Wilma moved inland and the surge was no longer sustained by the wind forcing. The height of the wave pulse exceeded 1.5 m in de-tided sea level data, but it was somewhat obscured in the surge measurements because of its propagating during the low tide. The duration of this wave pulse was ~6 hrs and the propagation speed varied within a range of 10-25 m s-1 indicating an evolution process of the initial disturbance. The wave pulse is identified as an edge wave with large spatial and temporal scales. Such relatively short-lasting waves induced by a hurricane on the continental shelf were not reported before. Most likely, they escaped detection, because a sparse spatial resolution in the standard observational network maintained by NOAA and USGS cannot resolve their phase propagation. Instead, the previous studies were focused on lower-frequency coastally trapped waves (CTW) with periods comparable to or longer than the inertial, which were thought to be prevailing wave modes generated by tropical cyclones. This project will investigate the generation and alongshore evolution of the hurricane-induced edge waves by means of process-oriented numerical modeling. More specifically, the following questions will be addressed: - What are the most favorable conditions for the edge wave generation by a hurricane landfall? The roles of the hurricane size, strength, translation speed and trajectory, as well as the role of shelf topography, will be delineated. - What topographic forms induce the local amplification of the edge waves? The effects of large topographic variations (widening/narrowing shelf, bending coastline, etc.) and smaller features (inlets, estuaries, capes, etc.) will systematically be studied. - What are the mechanisms of the edge wave dissipation? Is the dissipation mostly related with the bottom friction or with the offshore energy radiation? Broader impacts:The results of the project will have applications to national and regional security in such areas as hazard mitigation, disaster prevention, and the development of early warning systems. The results will also be important for coastal zone management and protection, as well as for maritime operations. One graduate student will be supported by this project.